General Development Plan 2008

Background Report on Sea Level Rise

April 2008

I. Introduction The average rate of sea level rise along Maryland’s coastline has been 3-4 mm/year, a rate nearly twice the global average. Sea level in the Chesapeake Bay area has risen approximately one foot in the last century and is predicted to rise another 2 to 3 feet by the year 2100 due to a combination of climate change and regional land subsidence (Leatherman et al., 1995). While the extent and range of impacts may vary, it is generally agreed that rising sea level threatens low-lying coastal plains making them vulnerable to erosion, flooding, inundation and salt water intrusion. As a causal force, sea level rise influences ongoing coastal processes, thereby increasing the vulnerability of coastal areas already under natural and human-induced stress. While Maryland will be subject to the full range of sea level rise impacts, risks associated with shoreline erosion, inundation, and coastal flooding pose the most significant threat.

A rise in sea level of the magnitude referenced above will have a significant effect on Anne Arundel County’s 520 miles of shoreline and low-lying coastal areas. The shoreline will change. Low-lying coastal areas such as Deale and Shady Side, already prone to high water tables, will likely experience expanded inundation. Areas currently inundated only periodically under storm and hurricane conditions may become permanently inundated as seawater migrates inland. Increased property damage due to standing water and flooding is possible. As sea level rises, so does the elevation of storm surge, further exacerbating the situation. Erosion will occur along the shoreline as it adjusts to encroaching seawater. The County’s fringe marshes and tidal wetlands will migrate inland in areas where topography remains relatively flat. Where the land rises sharply from the shore as it does along the Severn River with its characteristic cliff faces, tidal wetlands will be permanently submerged. These natural habitats serve as nursery grounds for many of the Chesapeake Bay’s living resources and are critical filters for reducing nutrient and sediment loads to the Bay. Shorelines will erode and in doing so will unleash tons of sediment that smothers near shore underwater grasses. When submerged aquatic vegetation disappears it no longer helps to buffer the shore against wave action, creating even more erosion.

Sea level rise has been referred to as the “ultimate planning challenge”. While sea level changes have played a historic role in shaping Anne Arundel County’s coastal environment, understanding how to address incremental and potentially significant changes in sea level is a difficult task. The challenge is further complicated by the broad spectrum of coastal issues and interests involved, as well as the inherent uncertainty associated with projecting accelerated sea level rise and its specific localized impacts. Despite these challenges it has become abundantly clear that coastal managers and planners must begin planning for sea level rise. II. Maryland’s Sea Level Rise Response Strategy Although global attention has only recently focused on climate change and sea level rise, planning for sea level rise is not new to Maryland. In 1999, Maryland’s Coastal Zone Management Program received a post-graduate fellow through the National Oceanic & Atmospheric Administration’s Coastal Services Center to develop a sea level rise response strategy for the State of Maryland. The Strategy was developed through: (1) an extensive review of related technology, data and research; (2) an assessment of Maryland’s vulnerability based on

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the range and magnitude of impact, the physical characteristics of the coastline, and population and growth patterns; and (3) an assessment of Maryland’s existing response capability.

The Strategy is comprised of the following four components each designed to build upon the other to achieve the desired outcome within a five-year horizon:

• Outreach & Engagement: Engage the general public, State and local planners, and

elected officials in the process of implementing a sea level rise response strategy. • Technology, Data and Research Support: Gain a better understanding of the regional

impacts of sea level rise and applicable policy response alternatives. • Critical Applications: Incorporate sea level rise planning mechanisms into existing state

and local management programs and ongoing coastal initiatives. • Statewide Policy Initiatives: Enhance, and where necessary, modify key State statutes to

remedy barriers and advance sea level rise planning initiatives. Outreach and Engagement Sea level rise issues have commanded a significant degree of public attention in recent years and the Maryland Department of Natural Resources continues to receive numerous requests for public presentations and workshops on the topic. In the past, the State used one-on-one interviews, issue forums, public presentations, a sea level rise display, field trips, and public workshops to foster a general understanding of sea level rise planning principles and to solicit input on the content and recommendations proposed in the response strategy. Despite these efforts, there remains a lack of understanding among the general public regarding the magnitude of sea level rise impacts and the connection between global climate change and sea level rise. Therefore, to build support for the implementation of a Sea Level Rise Response Strategy, the State has continued its active role in education of the general public. As the State continues to implement its Sea Level Rise Response Strategy, outreach efforts will expand to engage State and local planners and elected officials in the process of advance planning for sea level rise. The establishment of partnerships with select agencies and organizations is one of the primary means for ensuring effective application of sea level planning principles at the State and local level. Technology, Data and Research Support A substantial amount of research documenting both the magnitude of the sea level rise and its impact on Maryland’s coastal resources has greatly enhanced understanding of the regional implications of sea level rise. Though there is a sufficient knowledge base from which to move forward with policy responses in Maryland, a continued commitment to sea level rise research is still vital to the State’s ability to proceed. The State is committed to supporting sea level rise research whenever possible. Critical Applications A variety of State and local policies and regulations can be targeted in order to advance sea level rise planning principles. With political support local comprehensive plans, zoning ordinances, floodplain management ordinances, and capital facilities plans can be amended to address sea

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level rise issues. At the State level, efforts can be focused on capital facilities planning (e.g., State Highway Administration), and State-owned land management programs. In addition, the State can make great strides by including sea level rise issues in new and on-going coastal management initiatives. The goal would be to demonstrate successful application of sea level rise planning principles at the State and local level. Amending current policies and regulations to better address sea level rise and incorporating sea level rise issues into ongoing coastal initiatives are both critical to the State’s ability to accomplish this goal. Statewide Policy Initiatives By systematically targeting existing management frameworks, the State can develop a coordinated response. However, the State’s ability to fully develop a response capacity that comprehensively addresses the primary impacts of sea level rise, including the range of associated environmental and socio-economic impacts, hinges on the applicability of statewide policy frameworks. Enhancement and modifications to the Flood Control and Watershed Management Act, the Chesapeake Bay Critical Area Protection Act, the Wetlands and Riparian Rights Act, and the Economic Growth, Resource Protection and Planning Act will be necessary to successfully plan for sea level rise in the long-term. The Maryland Department of Natural Resources (DNR) is currently using the Sea Level Rise Response Strategy to guide its current sea level rise planning efforts and inform the Governor’s Commission on Climate Change. III. Governor’s Commission on Climate Change In 2007 Governor O’Malley, recognizing Maryland’s vulnerability to sea level rise and the need to take action, created The Governor’s Commission on Climate Change by signing Executive Order 01.01.2007.07 to advise the Governor and the General Assembly on matters related to climate change. To this end, the Commission is coordinating with the Maryland Departments of Natural Resources, Environment and Planning, and a comprehensive group of planners, emergency responders, environmental organizations, businesses and insurance representatives, to develop a strategy for reducing Maryland’s vulnerability to climate change, with an initial focus on sea level rise and coastal hazards. The Commission is supported by three work groups working to achieve the Commission’s charge of developing an action plan to address the causes of climate change, prepare for the likely consequences and impacts of climate change to Maryland, and establish firm benchmarks and timetables for implementing a Plan of Action. One of these work groups, the Adaptation Response Work Group has as its focus sea level rise. The work group is tasked with the development of a Comprehensive Strategy for reducing Maryland’s Climate Change Vulnerability. The Strategy will include recommendations for reducing the vulnerability of the State’s coastal, natural & cultural resources as well as strategies to address short and long term adaptation measures, planning and policy integration; education and outreach; performance measurements; and new or modified legislation that will strengthen and enhance the ability of the State and its local jurisdictions to plan for and adapt to the impacts of climate change.

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Emphasis is placed on working with local governments to identify their capacity to plan for and adapt to sea level rise, and where that capacity does not currently exist, to develop guidance to assist with identifying specific measures such as local land use regulations and ordinances to adapt to sea level rise and increasing coastal hazards. Further, the work group is to propose a timetable for the development of adaptation strategies to reduce climate change vulnerability among affected sectors, such as agriculture, forestry, water resources, aquatic and terrestrial ecosystems, and human health. IV. Integrated Planning for Sea Level Rise, Coastal Storms & Coastal Erosion Research conducted as part of Maryland’s Sea Level Response Strategy predicts that climate change and sea level rise will put Anne Arundel County’s citizens, property, natural resources, and public investments at risk. To protect Anne Arundel County’s future economic well-being, environmental heritage and public safety, an integrated approach must be taken to planning for and adapting to sea level rise, an increase in coastal storms, and resultant coastal flooding and erosion. Planning for and adapting to sea level rise should focus on three overarching themes: Avoidance, Accommodation/Adaptation and Protection. New Criteria for Identifying Priority Protection Areas Rising sea level will impact coastal ecosystems and natural resource lands. These resources provide wildlife habitats, have regional significance for migratory birds, sequester large amounts of carbon, provide sediment and nutrient water quality benefits, and generate economic benefits through farming, forestry, fishing and passive recreation. Identifying undeveloped lands and ecologically and economically important lands will be critical for targeted conservation and coordinated restoration in response to sea level rise and its associated effects. Preserving undeveloped, vulnerable lands also offers a significant opportunity to avoid placing people and property at risk to sea level rise and associated hazards including storm surge, coastal flooding and erosion in the future. As sea level rises, various future conditions are possible. As an example, tidal marshes have the potential to migrate landward if there are no barriers to migration, such as roads and buildings or other physical factors; or, they may be eliminated if the opportunity to migrate landward is blocked, or the rate of migration is exceeded by the rate of sea level rise. Identifying where these resources are, how important they are for various ecosystem values and economic services, and what the likely impact of sea level rise will be will provide the basic information needed to plan for the protection and management of them.

Sustainable Shoreline Management Practices Shoreline erosion is a significant issue that will worsen as a result of increased rates of sea level rise, and frequency and/or intensity of coastal storms from climate change. Comprehensive shoreline management should be an integral part of any future shoreline erosion control planning effort. A collaborative effort between State and local government to develop such plans will maximize the success of balancing protection of private property while minimizing disruption to the coastal environment. While hardening the shoreline is often viewed as appropriate from a landowner’s perspective, the effects on the Bay’s ecosystem are complex, difficult to quantify,

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and sometimes detrimental. Hardening the shoreline often eliminates important beach habitats, as well as the positive aspects of shoreline erosion such as accretion and beach nourishment, and can increase wave energy and turbidity, producing negative impacts on submerged aquatic vegetation. Hardening of shorelines over the long term eliminates the landward movement of marshes as a result of sea level rise and increases impacts on adjacent shorelines and property. Where site conditions are appropriate, “Living Shorelines” should be considered the preferred shore protection alternative. In addition to protecting the shoreline, living shorelines also trap sediment, filter pollution, and provide important habitat for both aquatic and terrestrial wildlife. Forest &Wetland Buffer Protection Forests and wetlands adjacent to the coast provide critical buffers for preventing damage to property subject to increased storm surge resulting from sea level rise. Adaptation strategies that identify options to prioritize retention and expansion of forests and wetlands in undeveloped, rural and developed areas will be beneficial in minimizing future shoreline erosion, reducing peak runoff during storm events and avoiding stranded infrastructure. Critical Areas, buffers, and other future impact areas could be targeted for forest establishment and expansion based on elevation and landscape planning. Future forest and wetland areas could provide replacement zones for wildlife migration and movement corridors. Coastal wetland ecosystems, such as salt marshes are particularly vulnerable to rising sea level because they are generally within a few feet of sea level. Wetlands provide habitat for many species, play a key role in nutrient uptake, serve as the basis for many communities’ economic livelihoods, provide recreational opportunities and protect local areas from flooding and property loss due to shoreline erosion. As the sea rises, the outer boundary of these wetlands will erode, and new wetlands will form inland as previously dry areas are flooded by higher water levels.

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The amount of newly created wetlands could be much less than the lost area of wetlands, especially in developed areas protected with bulkheads and rip rap revetments that prohibit new wetlands from forming further inland. Undeveloped areas within the Critical Area (1,000 feet of mean high tide), floodplain areas and areas of extensive wetlands are potential areas to target for expansion and preservation. Preserving these areas will minimize impacts associated with future development where sea level rise will be an issue. In addition to providing critical storm barriers, these forests and wetlands will provide additional climate change benefits through their ability to sequester carbon. Built Environment (Existing & Future) In addition to the impacts that sea level rise will have on the County’s natural environment, significant impacts on the built environment will be realized. Both residential and non-residential properties will experience the potential for inundation and increased flooding as well as the possibility of more frequent and stronger storms and associated storm surge. Public infrastructure including roads, bridges, culverts, sidewalks, storm drains, water and wastewater systems will also be impacted. Coastal inundation and flooding will result in economic damage, the precise form and magnitude of which are difficult to predict. Inundation, the total loss of property from permanent flooding when sea level rises above its current elevation, is expected to increase as is flooding which causes damage to non-inundated properties from episodic storm events. As sea levels rise, storm-related floodwaters and tidal surges will not have to rise significantly before causing damage. V. Study of Economic Impacts of Sea Level Rise In 2001, as a continuation of DNR’s larger sea level rise research efforts, DNR funded a study that investigated the magnitude and subsequent economic impact of sea level rise at the community scale. Using high-resolution elevation data derived from LIDAR, one, two and three foot elevation contours were developed to determine the potential reaches of sea level rise over a 100-year time frame within three “broadly representative” non-urbanized communities along the Chesapeake Bay. The Shady Side community in Anne Arundel County was one of the three communities studied. While the Study found that the risk of permanent inundation would affect relatively few properties, the risk of increased flood damages is great. Even small increases in sea level rise could substantially increase damages particularly in densely populated vulnerable areas on the western shore by raising base flood elevations and expanding the 100-year floodplain. The following table provides vulnerability data specific to the Shady Side community.

Table 1. Summary of Vulnerable Properties under a 3-foot Sea Level Rise in the Shady Side Community

Area 3.75 sq. mi. (1,800 acres) Elevation Below 3 ft. (%) 1%

Total # of Properties 2,120 Properties in FEMA100-year flood zone (%) 42%

Miles of Road below 3 ft 1 mile Wetlands Threatened 118 acres

Projected Population Growth (%) (By2030) 16% Source: The Economic Cost of Sea Level Rise to Three Chesapeake Bay Communities, August 2004

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The Economic Cost of Sea Level Rise to Three Chesapeake Bay Communities analysis of “at risk” properties was framed by the following set of assumptions: sea level rise was assumed to be non-accelerating, meaning that a 2 or 3-foot rise would occur uniformly from the present until the year 2100; no further protection of the shoreline (i.e. bulkheads) in response to sea level rise will occur; there would be no upland migration of wetlands; there would be no increase in storm severity or frequency, and, there would be no new development within identified flood zones. Based on these assumptions, economic losses were calculated over a one hundred year time span for the following set of damage categories: residential inundation, residential flood loss, non-residential inundation loss, infrastructure costs, and lost wetland services. Economic losses that occur in the future were calculated using constant value dollars (Year 2000) and discounted to present values using a 2% discount rate. The figures reported in the following study results refer to the discounted costs. The authors of the Study noted that by applying the discount rate of 2%, they made an intentional decision to err on the side of making conservative damage estimates. The Economic Analysis projected impacts under a sea level rise scenario of two and three feet over the next one hundred years. It was assumed that sea level would rise 2 feet by the year 2050 and 3 feet by the year 2100. Results were presented for the four damage categories: inundation of improved residential properties; increase in episodic flood damages; roads and bridges; and wetland loss. Inundation of Improved Residential Properties A two-foot rise in sea level over the next century will inundate one currently improved residential property in Shady Side. If the forecast of three feet of sea level rise were to occur the number of residential properties inundated would rise to 11. Under a two-foot level rise scenario, the economic loss projected for the improved property is estimated at $38,000. Under a three-foot sea level rise scenario projected economic losses of improved residential property would be nearly ten times greater in Shady Side at an estimated $350,000. Increase in Episodic Flood Damages Increased episodic flood damages are projected to affect a much greater number of structures than inundation and much sooner. Whereas one structure was predicted to be impacted by inundation in Shady Side in the two-foot rise scenario, 903 properties would experience periodic flooding in the two foot rise scenario. Increased damages due to an increase in episodic flooding were calculated based on an estimation of increased flood insurance premiums for existing structures in the 100 year flood plain as designated by the National Flood Insurance Program. For Shady Side this translates into $12.9 million. However, as demonstrated by Hurricane Isabel, damages resulting from a single storm event can greatly outweigh those predicted over a 100-year time span. Roads & Bridges Neither a two nor three-foot rise in sea level is predicted to have significant impact on roadways in Shady Side. A two-foot rise in sea level would inundate less than two-tenths of a mile of road. A three-foot rise would inundate approximately one mile. Although the length of roadway inundated is only approximately one mile, the location of the inundation is critical in that Shady Side is located on a peninsula with only a single road providing access into and out of the

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community. While the Study established that road inundation would occur, it did not identify the depth of inundation or whether the roads may remain passable. Nonetheless, it can be assumed that an inundated road would need to be raised and retrofitted. Wetland Losses Wetland losses in Shady Side are anticipated to be 61 acres under a two-foot rise scenario. A three-foot rise in sea level would increase wetland losses to 118 acres. Damage estimates were based on an estimation of the loss of public benefits from the functions of those wetlands rather than their market value as real estate. The functional benefits of wetlands include improving water quality and providing habitat for fisheries. Based on a literature review, the economic analysis assigned an annual benefit of $350 to each acre. Economic losses were determined by calculating a projected year of inundation, and then multiplying $350 times the acres lost times the number of years remaining in the century. This translates into estimated losses of $142,000 under the two-foot scenario and $362,000 with three feet of rise in Shady Side. The study reports that quantifying the non-market value of such things as wetlands is a subject of controversy in environmental economics. Therefore the value assigned to loss of wetlands services should be carefully interpreted. VI. Western Shore Maryland Hurricane Evacuation Study The U.S. Army Corps of Engineers, Baltimore District recently completed a Hurricane Evacuation Study (HES) for the Maryland Western Shore including Anne Arundel, Baltimore, Charles, Calvert, Harford, Prince George’s, and Saint Mary’s Counties and Baltimore City. The study was conducted using the National Weather Service – National Hurricane Center’s SLOSH Model (Sea, Land and Overland Surges from Hurricanes) to estimate the limits of potential tidal flooding from Categories 1 through 4 hurricanes. The results are illustrated on the Storm Surge Map shown in Figure 1. This map indicates areas of possible tidal flooding from hurricanes together with areas of potential freshwater flooding based on FEMA Flood Insurance Rate Maps for 100-year and 500-year floods. Although the storm surge elevations predicted by the model represent a “worst case scenario”, the results are useful as a planning-level study to aid in future decision-making related to infrastructure and major public and private investments. The County’s Office of Emergency Management also works with the U.S. Army COE in using the study results to develop its emergency operations plans. This effort has included the creation of a network of approximately 60 evacuation zones and specified transportation routes to be used in the event of a hurricane or flooding emergency. The County will continue to work with the Corps and the Maryland Emergency Management Agency in maintaining the most up-to-date data for use in emergency planning. VII. Conclusion & Future Needs Based upon the economic research conducted to date on the Shady Side community and current climate change predictions for the Chesapeake Bay area, is it apparent that Anne Arundel County will experience impacts from sea level rise. Initiating the development of an integrated planning

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Figure 1

and implementation strategy now will position the County to successfully adapt to the impacts of sea level rise and minimize future associated damages. The County’s General Development Plan should recommend an integrated planning strategy that, at a minimum, addresses potential threats in at-risk areas and proposes strategies for a phased implementation response to achieve either avoidance or reduction of impacts, under the following categories: • Land use, zoning, and population density regulations to reduce population and

investments at risk;

• Public and market-based incentives/disincentives to reduce property damage and threats to human health;

• Planning for community infrastructure such as roads, schools, public safety and medical

facilities, water and wastewater systems, gas, electrical and communications utilities to ensure public safety; and

• Maintenance of existing and future natural resource lands, wildlife habitat, and

agricultural lands to minimize impacts from storm surge.

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References

Titus, J.G.1991. Green House Effect and Coastal Wetland Policy. Environmental Management 15(1): 39 – 58. Johnson, Z.P. 2000. A Sea Level Rise Response Strategy For The State of Maryland. Maryland Department of Natural Resources, Annapolis, Maryland. The Maryland Commission on Climate Change. 2008. Climate Action Plan: Interim Report to the Governor and the Maryland General Assembly. Maryland Department of Natural Resources. 2004. Summary and Analysis of The Report: “The Economic Cost of Sea Level Rise o Three Chesapeake Bay Communities”. Revised. 2003. Michael, J.A., D.A. Sides, and T.E. Sullivan. Annapolis, Maryland

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